Safe wafer pick-and-place is a very important technical indicator for integrated circuit production lines. Generally, the breakage rate of wafers due to wafer handling equipment in the course of production should be less than 0.001%. Compared with a single-wafer processing system, a batch-type wafer heat treatment system requires more wafer transfer and pick-and-place operations in each production process, which makes higher demands of safe and reliable wafer transfer and pick-and-place.
Nowadays, robots have been widely applied in the field of semiconductor IC manufacturing technology and have become important tools in wafer handling systems for picking, placing and transferring unprocessed and processed wafers. The robot can response to instructions to accurate move to a point of wafer location in a three-dimensional or two-dimensional space to pick and place wafers.
Currently, the positional parameters of the robot during handling a wafer in the batch-type wafer heat treatment equipment are generally obtained by offline teaching. The offline teaching data of the positional parameters are usually stored in a memory and calibrated periodically. The robot uses its fork to perform the pick-and-place operation to the wafers located in a wafer carrier according to the stored offline teaching data. However, factors such as robot fork rotation or positional offset may cause collision of the robot fork with the wafer or wafer carrier when the robot performs the pick-and-place operation, resulting in irreparable losses such as damages to the wafer or equipment.
Accordingly, in order to perform the wafer pick-and-place operation, an accurate pose recognition for the robot fork is required, such that proper measures can be taken to the fork which is in the abnormal condition to ensure a safe pick-and-place operation.